Pneumatic tire with band element having tapered end portions

ABSTRACT

A run flat pneumatic tire has a thin annular band embedded in a crown portion of the tire. The band preferably is a composite member formed of a plurality of layers elongated strip material providing the band with inner and outer annular axially extending surfaces terminating in a pair of outer end portions. Either one or both of the outer end portions are tapered toward the other end portion and toward a pair of end edges to reduce interlaminar shear. The end edges can be straight or rounded surfaces and the tapered outer end portions may be coated with fiber filled epoxy coating.

BACKGROUND OF THE INVENTION TECHNICAL FIELD

The invention relates to reinforced resilient pneumatic tires and moreparticularly to a vehicle tire reinforced by a thin annular compositeband which enables the tire to run in an unpressurized condition and toprovide greater puncture resistance for the tire. More particularly, theinvention relates to a pneumatic tire in which the internal band elementis formed to resist interlaminar shear stresses and provide enhancedinflated and uninflated banded tire durability and puncture resistance.

BACKGROUND INFORMATION

Various tire constructions have been devised over the years which enablea tire to run in an under-inflated or non-inflated condition, such asafter receiving a puncture and loss of pressurized air, for extendedperiods of time and at relatively high speeds. This enables the vehicleoperator to safely drive the vehicle to an appropriate location forrepair or replacement of the punctured tire. Certain of these safetytires, referred to as "run flat tires", have been successful for certainapplications and certain types of tire constructions. Most of these runflat tires achieve their run flat capability, by the placement ofreinforcing layers or members of relatively stiff elastomeric materialin the side walls of the tire which enable the tire to support thevehicle weight even with the complete loss of internal air pressure.Examples of such prior art run flat tire constructions which use suchsidewall inserts are shown in U.S. Pat. Nos. 3,911,987; 3,949,798;3,954,131; 4,067,372; 4,202,393; 4,203,481; 4,261,405; 4,265,288;4,287,924; 4,365,659; 4,917,164; and 4,929,684.

In addition to these prior art run flat tires, various run flat tireconstructions have been developed which utilize a thin annular bandwhich extends circumferentially throughout the tire beneath the treadarea. Examples of such banded run flat tires are shown in the followingpatents.

U.S. Pat. No. 4,428,411 describes a method to make a particular band foruse in a run flat tire which uses a series of side-by-side elements inthe form a helix. The band has hoop compression as against aconventional breaker belt that has no significant compressive strengthbut is used only to resist tension loads endured by the tire whenpressurized.

U.S. Pat. Nos. 4,673,014 and 4,794,966 teach a method to acquiredesirable prestressing in a fabricated band made of helical elements.Physically bending the larger diameter helix element around a smallermandrel and securing it with a resin impregnated tape acquires adesirable level of prestressing.

U.S. Pat. No. 4,456,048 teaches a method of acquiring a change in bandstiffness as a function of deflection. The band has a lower stiffnessfor normal pressurized operation and has a higher stiffness to supportload when the tire is uninflated and experiences larger deflection.

Japanese Patent application No. JP 63141809 discloses a run flat tirehaving a banded element which is formed of layered strips of materials,such as an arramed filament which is impregnated with a high elasticityepoxy resin, which after hardening provides a stiffened band. The tireof this disclosure requires that elastomeric side wall inserts beutilized in combination with the band in order to achieve the desiredrun flat characteristics.

Other run flat banded pneumatic tires are shown in U.S. Pat. Nos.4,111,249; 4,318,434; 4,428,411; 4,459,167; and 4,734,144.

Banded tires have been fabricated with band materials made of steel,aluminum, titanium, and epoxy and thermoplastic composites with glass,KEVLAR (aromatic polyamide) and graphite fiber reinforcement. The commonfailure mode with such lightweight, economical laminate bandconstructions is interlaminar shear within the band's primary bendingneutral axis. This is a fatigue failure and is directly related to thespectrum of cyclic operating stress. As in all fatigue failures, thelower the stress, the longer the operating life. This problem of fatiguefailure occurring along the neutral axis of the band resulting ininterlaminar shear can be reduced by the prestressing the band duringits manufacture, as described in U.S. Pat. No. 5,879,484.

Numerous prior art pneumatic tires have been provided with an annularband usually of metal, to resist puncture by sharp objects protrudingthrough the tread area. Although these prior art puncture resistanttires utilizing a metal band provide the desired puncture resistance, inmost cases, the metal band effects the ride characteristic of the tireand the life expectancy thereof.

Thus, it is desirable to provide a band element for run flat pneumatictires and for pneumatic tires having greater puncture resistance, withincreased resistance to interlaminar shear stress in the inflateddeflected banded tire, the uninflated deflected banded tire and thecondition of a banded tire encountering a road surface anomaly, which isaccomplished without materially increasing the difficulty of themanufacturing process for producing the band element and withoutmaterially increasing the cost thereof. The band element of the presentinvention achieves these results.

SUMMARY OF THE INVENTION

Objectives of the invention include providing an improved pneumatic tirethat is substantially similar in ride, comfort, durability and operationas conventional pneumatic tires, yet which is able to be operated safelyat reasonable speeds and for a sufficient number of miles after loss ofinternal pressurization.

Another objective of the invention is providing such a pneumatic tireand band element therefor which has enhanced load carrying capability,improved endurance by minimizing band stress, and in particularminimizes interlaminar shear stresses heretofore resulting indestruction of the band element.

Another objective of the invention is to provide such a band elementwhich has enhanced inflated durability achieved by increasing theinterlaminar shear strength of the band by reducing circumferentialstrain and circumferential stress which is achieved by contouring of theband edges, and in which the enhanced durability is derived independentof other preferred band dimensions such as diameters, modulus ofelasticity, prestressing of the band, etc.

A still further objective of the invention is to provide such a bandelement which reduces interlaminar shear by contouring of the bandelements irrespective of whether the band element is fabricated ofmaterials such as laminated metals, thermoplastic and thermosettingmaterials and multi-layer composites and is applicable to passengertires, light truck tires, racing tires and tires with and/or withouttread patterns.

Another objective of the invention is to provide such a run flat tirewhich has increased puncture resistance from the tread contacting roadhazards, which can be manufactured at a cost and weight competitive withconventional non run flat tire constructions and which will permit theelimination of a spare tire conventionally required in automobilesthereby providing a cost saving to vehicle manufacturers and owners.

A further objective of the invention is to provide such a band elementin which the interlaminar shear strength is increased by coating thetapered outer end portions with a graphite fiber filled epoxy resin.

These objectives and advantages are improved by a thin annular band forembedding in the crown portion of a pneumatic tire, said band having anaxial width and a radial thickness with a neutral axis extendinggenerally through the center of the band in an axial direction, saidband being a composite member formed of a plurality of layers of anelongated strip material and having inner and outer annular axiallyextending surfaces terminating in a pair of outer end portions and apair of end edges with certain of said end portions being tapered towardsaid pair of end edges.

These objectives and advantages are further obtained by a pneumatic tirehaving an elastomeric casing with a tread portion formed in a crownportion thereof and sidewalls extending from the crown portion togenerally annular beads adapted to normally seat themselves in an airtight secured relationship with a wheel; an annular band embedded in thecrown portion having an axial width and a radial thickness with aneutral axis extending generally through the center of the band in anaxial direction, said band being a composite member formed of aplurality of layers of elongated strip material and having inner andouter annular axially extending surfaces terminating in a pair of outerend portions and a pair of end edges with certain of said end portionsbeing tapered toward said pair of end edges.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention, illustrative of the best modesin which applicants have contemplated applying the principles, are setforth in the following description and are shown in the drawings and areparticularly and distinctly pointed out and set forth in the appendedclaims.

FIG. 1 is a sectional view of a prior art run flat tire having a bandelement incorporated therein;

FIG. 2 is a sectional view similar to FIG. 1 showing the improved bandelement incorporated within a run flat tire;

FIG. 3 is a perspective view of the improved band element of the presentinvention;

FIG. 4 is a greatly enlarged fragmentary view of the edge of the bandelement taken on line 4--4, FIG. 3;

FIG. 5A is an enlarged fragmentary elevational view similar to FIG. 4;

FIGS. 5-12 are enlarged fragmentary sectional views of variousembodiments of band elements having different end and edgeconfigurations;

FIGS. 13 and 14 are enlarged fragmentary sectional view of twoadditional embodiments of band elements mounted within the tread of arun flat tire; and

FIG. 15 is a greatly enlarged fragmentary elevational view of the righthand end of FIG. 11 having a coating of a graphite fiber filled epoxythereon.

Similar numerals refer to similar parts throughout the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The improved pneumatic tire of the present invention containing theunique band element is indicated generally at 1, and is shown in crosssection in FIG. 2. Most of the components of tire 1 are of aconventional design and construction such as shown in the prior artbanded tire of FIG. 1 indicated generally at 2. Tire 1 as well as tire 2consists generally of a pair of beads 3 which are adapted to be seatedin an air tight relationship on a wheel (not shown). Tires 1 and 2further have a carcass or casing 4 having an outer peripheral treadportion 5 formed in a crown region thereof, and sidewalls 7 extending onboth sides from the crown portion to beads 3. Tread 5 is formed with ausual tread pattern depending upon the particular characteristics to beachieved by the pneumatic tire and the particular vehicle on which thetire will be mounted.

Sidewalls 7 of the casing are reinforced by usual radial reinforcingelements 8 which extend throughout the sidewalls and are turned up aboutbeads 3. As is well known in the art, sidewall plies are reinforcedfibers composed of rayon, nylon, polyester, steel and other types ofknown materials. These sidewall reinforcements extend from at least thecrown portion of the tire and throughout the sidewalls to the bead areathereof.

In accordance with one of the main features of the present invention, animproved annular stiffening band indicated generally at 10, is mountedwithin the crown portion of the tire radially beneath the tread andextends circumferentially throughout the tire and extends generallythroughout the width of the tread. Band 10 is operatively connected tothe sidewall reinforcing elements 8 either physically or through theintervening elastomeric material of the crown portion and tread whichbonds the band to the reinforcing elements and radially stabilizes theband. Band 10 is relatively thin in contrast to its width and can rangein width between 6 and 12 inches and in thickness generally between 0.1and 0.2 inches depending upon the particular tire in which it is bonded.It is also understood that tire 1 will have a usual innerliner, gumabrasive strips and other components present in a conventional pneumatictire which are not shown in FIG. 1 or discussed in further detail.

As discussed above, the main object of the invention is the formation ofband 10 so as to provide sufficient load carrying capability withimproved endurance by eliminating or materially reducing interlaminarshear by simple contouring of the band edges. As described in U.S. Pat.No. 5,879,484, the problem of fatigue failure occurs along the neutralaxis 12 as the band element undergoes cyclic stresses both when in theinflated and uninflated conditions as the central footprint region ofthe tire and adjacent band element conforms to the road surface for ashort distance on either side of the center of the tire. The change inthe band element axial geometry from circular to flat causes a change inthe stress/strain regime within the band element caused by flattening ofthe band element. Consequently, in the central footprint region, thefibers along the inside diameter of the band element are in tension andelongate while the fibers along the outside diameter of the band elementare in compression and are shortened. These forces are experienced tothe greatest degree along the axis of the band element ultimatelyresulting in interlaminar shear of the band element beginning at theneutral axis thereof.

The radius of the band element is largely determined by the tire sizeand thus can be changed only within narrow limits. The band elementradial thickness will be determined so as to give acceptable bandelement outer fiber endurance as experienced by those fibers alternatingbetween tension and compression. Banded tire durability including bothinflated and uninflated conditions is limited by the interlaminar shearstrength of the band element. More specifically, band element durabilitylimited by failure due to interlaminar shear initiates near the axialends of the band element along the neutral axis and progresses towardsthe axial center of the band element. Thus, it has been found to beadvantageous to decrease interlaminar shear stress near the axial endsof the band element and thereby improve band element durability. This isachieved in the present invention as described further below, bymodifying the geometry of the axial ends of the band element whichdecreases the band element radial thickness only near the axial ends ofthe bands in order to lower the tension and compressive stresses in theouter band element fibers and consequently decreases interlaminar shearin these regions.

In the preferred embodiment, the band element is a composite monolithicstructure made of many layers as shown diagrammatically in FIG. 4. In amicro sense, the band element consists of a finite number of layers witheach layer being made up of a finite number of widths of tape placed ina side-by-side fashion and with each tape being made of a combination ofmany fibers embedded in a suitable resin or matrix such as described inpending patent application Ser. No. 08/782,364 now U.S. Pat. No.5,879,484 and Ser. No. 09/120,210 now allowed, the contents of which areincorporated herein by reference. It has been found that decreasing bandelement radial thickness near the axial ends of the band element isespecially important for the preferred multilayered composite bandelements because of two important factors.

Monolithic composite band elements don't develop full strength intension, compression or interlaminar shear within approximately 0.50 to1.00 inches from the axial ends of the band element. These end effectsare attributable to fiber wetting, void ratio, manufacturing, handlingand processing of the band element. Monolithic multi-layer compositeband elements have lower interlaminar shear strength vs. band elementsmade of steel, aluminum or homogeneous resin/fiber composites. Thereason for this is that the shear strength of a multi-layer compositeband element is lower between the layers vs. within the layers. Thus,the interlaminar shear failures comer tend to initiate at the interfacebetween the layers near the neutral axis.

This reduction in the radial thickness of the axial ends of the bandelement in order to minimize interlaminar shear stress can be obtainedby various configurations as shown in FIGS. 5-12. Referring initially toFIG. 3, band element 10 has inner and outer axial surfaces indicated at14 and 15 respectively, which terminate in a pair of end edges 17 and18. Band element 10, shown in FIGS. 3, 4 and 5, is formed with taperedouter end portions 21 and 22 formed only on outer surface 15 of band 10.Referring to FIG. 5A, this angle of taper A preferably is generallywithin the range of between 5° and 45° with the axial length of endportions 21 and 22 indicated by B, being generally within the range ofbetween 3% and 15% of the total axial length L of the band element.Alternatively, this can be indicated as d being generally within therange of one-fourth and three-fourth, of thickness t. Also, it was notedthat the outer end edges 17 and 18 are generally flat radially extendingsurfaces.

Another embodiment 20 is shown in FIG. 6 wherein tapered end portions 21and 22 are formed only along inner surface 14 with edges 17 and 18 alsobeing generally flat radially extending surfaces.

A modified band 30 is shown in FIG. 7 in which the tapered end portions21 and 22 are formed in both the inner and outer surfaces 14 and 15 withend edges 17 and 18 being generally flat radially extending surfaces.

FIG. 8 shows a further modified band embodiment 40 in which inner andouter surfaces 14 and 15 are substantially parallel and flat throughoutthe entire axial length but with the end edges 41 and 42 being roundedwhich also have been found to reduce interlaminar shear even though thetapered end portions are merely the end radiuses 43 and 44 of the endedges.

Another embodiment of band element is indicated at 50, and shown in FIG.9 in which inner surface 14 is generally substantially flat throughoutits entire axial length with outer surface 15 having a tapered outer endportion 21 similar to that shown in FIG. 5 with the main differencebeing that the outer end edges 51 are generally rounded.

FIG. 10 shows a further modified band 60 similar in many respects to theembodiment 20 of FIG. 6 wherein the tapered end portions are formed onlyon inner surface 14 with the main difference being that the outer endedges 61 are rounded and are not generally flat radial extendingsurfaces as shown in band 20 of FIG. 6.

FIG. 11 shows a still further modified band element 70 which is similarin most respects to that of embodiment 30 of FIG. 7 wherein inner andouter surfaces 14 and 15 are generally flat and parallel with eachother, but with both tapered outer end portions 21 and 22 terminating inround edges 70 instead of the generally flat radial extending surfaces17 of band 30 of FIG. 7.

FIG. 12 shows another band 80 which has a generally continuous curvedconfiguration with outer surface 15 being generally convex throughoutits entire length with inner surface 14 being concave but at a slightlyreduced radius of curvature so that the end portions 21 and 22 aretapered toward each other and preferably terminate in round edges 81although the same could be generally flat radial extending surfaces asthose shown in FIGS. 5, 6 and 7, without affecting the concept of thepresent invention.

A modified pneumatic tire construction is indicated generally at 100,with only a small cross sectional portion of the crown area 101 beingshown in FIG. 13. In this embodiment, three narrower band elementsindicated generally at 102, are embedded within the crown portion andare in axial alignment therewith and separated by an intervening space103. Band elements 102 can have the configuration of any of the bandelements 20, 30, 40, 50, 60, 70 and 80 with only the configuration ofband element 70 being shown therein. The only difference between theband elements of pneumatic tire 100 and those of tire 2 is that theaxial lengths thereof are materially reduced to approximately 1/4 theaxial length of the band elements shown and described above which extendsubstantially continuous throughout the axial length of the tire.

A further modified pneumatic tire is shown in FIG. 14 and is indicatedat 200. Three band elements 201 are shown incorporated within the crownportion 202 thereof and are similar to that described above with respectto tire 100 with the main difference being that the outer two bandelements 201 and 203 are in axial alignment with each other with theintermediate band element 202 being spaced radially from neutral axis 12and with its ends in overlapping relationship to adjacent ends of theaxial aligned bands 201 and 203. Again, the particular configurations ofband elements 201, 202 and 203 shown in FIG. 14 are similar to bandelement 70 described above but can assume the configurations of theother band elements shown in the drawings and described above withoutaffecting the concept of the invention. Likewise, the number of bandelements and their particular alignment within the crown portion of apneumatic tire can also vary without affecting the concept of thepresent invention.

A still further modified embodiment is shown in FIG. 15 and is indicatedgenerally at 300. Band element 300 is generally similar to the end ofthe band shown in FIG. 11 although the following discussion isapplicable to any of the bands shown in the drawings and describedabove. The tapered end portions 21 and 22 of band element 300 are coatedwith an epoxy filled with a strengthening fiber arranged in a randomorder such as graphite, which will further enhance the interlaminarshear strength of the band. Other types of fiber filled epoxy coatingsother than graphite can be used without affecting the concept of thisfeature.

In summary, the dominant mode of durability fatigue for the band elementin banded tires has been described and simple modification to the axialends of the band element has been shown and described which can reducethe level of strain in the inner fibers of the band element near theaxial ends and more importantly this modification can reduceinterlaminar shear stress at the neutral axis near the axial ends of theband element thereby reducing the interlaminar shear throughout theaxial length of the band element thereby increasing durability of theband element and pneumatic tire in which it is incorporated.

Accordingly, the improved band element for pneumatic tire is simplified,provides an effective, safe, inexpensive, and efficient device whichachieves all the enumerated objectives, provides for eliminatingdifficulties encountered with prior devices, and solves problems andobtains new results in the art.

In the foregoing description, certain terms have been used for brevity,clearness and understanding; but no unnecessary limitations are to beimplied therefrom beyond the requirement of the prior art, because suchterms are used for descriptive purposes and are intended to be broadlyconstrued.

Moreover, the description and illustration of the invention is by way ofexample, and the scope of the invention is not limited to the exactdetails shown or described.

Having now described the features, discoveries and principles of theinvention, the manner in which the improved band element for pneumatictire is constructed and used, the characteristics of the construction,and the advantageous, new and useful results obtained; the new anduseful structures, devices, elements, arrangements, parts andcombinations, are set forth in the appended claims

We claim:
 1. In a pneumatic tire including an elastomeric casing with atread formed in a crown portion thereof and sidewalls extending from thecrown portion to generally annular beads adapted to normally seatthemselves in an airtight secured relationship with a wheel; an annularband embedded in the crown portion having an axial width and a radialthickness with a neutral axis extending generally through the center ofthe band in an axial direction, said band being a composite memberformed of a plurality of layers of elongated strip material and havinginner and outer annular axially extending surfaces terminating in a pairof outer end portions and a pair of end edges with certain of said endportions being tapered toward said pair of end edges.
 2. The pneumatictire defined in claim 1 in which a plurality of said bands are embeddedin the crown portion.
 3. The pneumatic tire defined in claim 2 in whichthree bands are embedded in the crown portion and are axially alignedwith each other.
 4. The pneumatic tire defined in claim 2 in which threebands are embedded in the crown portion, wherein two of said bands areaxially aligned with each other and a third band is spaced radiallyoutwardly from and intermediate said two aligned bands.
 5. The pneumatictire defined in claim 4 in which the outer end portions of theintermediate band overlap one of the outer end portions of each of theaxially aligned bands.
 6. The pneumatic tire defined in claim 1 in whichonly the outer end portions of the inner surface of the band are taperedtoward the end edges.
 7. The pneumatic tire defined in claim 1 in whichonly the outer end portions of the outer surface of the band are taperedtoward the end edges.
 8. The pneumatic tire defined in claim 1 in whichthe end edges are generally flat radially extending surfaces.
 9. Thepneumatic tire defined in claim 1 in which the end edges are rounded.10. The pneumatic tire defined in claim 1 in which the outer endportions of the band have a fiber filled epoxy coating applied thereto.11. The pneumatic tire defined in claim 10 in which the fiber filling isgraphite.
 12. The pneumatic tire defined in claim 1 in which each saidtapered end portion has an angle of taper generally within the range ofbetween 5° and 45°.
 13. The pneumatic tire defined in claim 1 in whichthe annular band has an axial length (L); and in which each said taperedend portion has an axial length generally within the range of between 3%and 15% of said axial length (L) of said band.